Act disgusted

"Jesus Christ, this was really bad. Absolutely disgusting, we're fucking cousins!"

"Yeah," Sarah says, seeming reassured.

"We can never talk about this again," you say.

"You're right, definitely," Sarah nods. "Let's just ignore this, and never mention it again."

You nod in response.

"OK, I gotta go. I need to get the fuck out of here," Sarah says, before hurrying off down the hallway, leaving you alone.

"Jesus, that was surprising. And weird as shit," you mutter, although you do note in the back of your head that she was a surprisingly good blowjob. "Fuck it, I gotta get to class anyway."